linux-kernel - Re: [PATCH] LinuxPPS (with new syscalls API)

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Message-ID: <20070627101449.GH13886@enneenne.com>
Date:	Wed, 27 Jun 2007 12:14:49 +0200
From:	Rodolfo Giometti <giometti@...eenne.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] LinuxPPS (with new syscalls API)

On Tue, Jun 26, 2007 at 06:38:40PM +0100, David Woodhouse wrote:
> 
> 64-bit kernels can run 32-bit userspace programs. But some structures
> come out _differently_ between 32-bit and 64-bit compilation, so the
> system call needs a special 'compat' handler instead of just running the
> normal 64-bit system call.
> 
> The 'struct timespec' is one structure which is sometimes different for
> 32-bit vs. 64-bit, so any system call taking a 'struct timespec' must
> have a separate compat_sys_xxxx() to handle that. See something like
> compat_sys_clock_settime() in kernel/compat.c for an example (but don't
> use set_fs() like it does; just see how it handles the compat_timespec).

Did you mean something like this?

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index befe292..3e401e5 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -26,6 +26,7 @@
 #include <linux/init.h>
 #include <linux/linkage.h>
 #include <linux/sched.h>
+#include <linux/compat.h>
 #include <linux/pps.h>
 #include <asm/uaccess.h>
 
@@ -284,9 +285,15 @@ sys_time_pps_getcap_exit:
        return ret;
 }
 
+#ifdef CONFIG_COMPAT
 asmlinkage long sys_time_pps_fetch(int source, const int tsformat,
-                                       struct pps_info __user *info, 
-                                       const struct timespec __user *timeout)
+                               struct pps_info __user *info, 
+                               const struct compat_timespec __user *timeout)
+#else
+asmlinkage long sys_time_pps_fetch(int source, const int tsformat,
+                               struct pps_info __user *info, 
+                               const struct timespec __user *timeout)
+#endif
 {
        unsigned long ticks;
        struct pps_info pi;
@@ -318,7 +325,11 @@ asmlinkage long sys_time_pps_fetch(int source, const int ts 
        /* Manage the timeout */
        if (timeout) {
+#ifdef CONFIG_COMPAT
+               ret = get_compat_timespec(&to, timeout);
+#else
                ret = copy_from_user(&to, timeout, sizeof(struct timespec));
+#endif
                if (ret)
                        goto sys_time_pps_fetch_exit;
                if (to.tv_sec != -1) {

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail:    giometti@...eenne.com
Linux Device Driver                             giometti@...dd.com
Embedded Systems                     		giometti@...ux.it
UNIX programming                     phone:     +39 349 2432127
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